Registers – Coded record sensors – Particular sensor structure
Reexamination Certificate
2000-02-17
2001-06-12
Frech, Karl D. (Department: 2876)
Registers
Coded record sensors
Particular sensor structure
C235S462320, C235S473000
Reexamination Certificate
active
06244509
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to scanning devices for capturing information, for example images from paper carriers, and is particularly, but not exclusively, concerned with scanning devices for capturing information on financial instruments such as banknotes of various types.
DESCRIPTION OF THE PRIOR ART
Various scanning devices for capturing information on paper image carriers are known. The most well known devices are hand-held scanners for reading bar codes, e.g. one patented under USSR Inventor's Certificate No. 1837334. That device contains a light source, a converging lens, an aperture diaphragm and diaphragm-coupled light receiver, all optically coaxial. A spherical lens is mounted between the scanned carrier and the aperture diaphragm. Such device may have the form of a ballpoint pen-like rod and be of a fairly simple design. The functionality of such a device, however, is limited to reading bar codes, its accuracy, resolution and operation speed being insufficient for other purposes. Other hand-held apparatuses—more sophisticated in design and having expanded functionalities—are also known (e.g. U.S. Pat. No. 5,349,172, U.S. Pat. No. 5,354,977, WO 94/19766 and WO 94/19764). Those devices use LED arrays to illuminate the carrier scanned and CCD arrays to take in reflected signals. Such devices, however, do not have sufficient functionality for scanning in large amounts of information when necessary.
Also known are desk-top scanning devices for capturing images and printed information. Such devices contain an optical unit comprising a light source, a light guide, a focusing and/or filtering optical element system, a light receiver and an A-D converter processing signals from the light receiver (e.g. Russian Federation Patent No. 2032217 and U.S. Pat. No. 5,295,196).
The deficiencies of known devices consist in their design complexity and the illuminator's excessive power consumption. The complexity of design is primarily the result of the sophisticated optical system which uses lenses, mirrors, etc. as focusing elements which are challenging in manufacture and require precise adjustment for correct operation of the device. Moreover, in order to obtain reflected luminous flux of sufficient intensity, a great amount of light energy is required to illuminate the information carrier.
WO99/18536 describes a much simpler scanning device which has been found to be very successful. However, we have realised that this device is not so far being utilized to its full ability.
SUMMARY OF THE INVENTION
In accordance with the present invention, a scanning device for capturing images, contains an optical unit comprising a light source, a light guide, and a light receiver, wherein the light guide comprises a substantially parallel sides, transparent member, the member having first opposed ends extending between the parallel sides, one of the ends facing the light source and extending non-orthogonally between the parallel sides, the other end facing the image to be scanned in use, and second opposed ends extending between the parallel sides and the first opposed ends; whereby light from the light source enters the light guide through the one first end, is directed onto the image after passing out of the other first end, is reflected back into the light guide and then directed by the light guide towards the light receiver, the arrangement being such that one portion of the reflected light passes to the light receiver without being reflected by the second opposed ends while another portion of the reflected light passes to the light receiver after being reflected by one or both of the second opposed ends, the two portions being directed to different parts of the light receiver, the device further comprising a filter through which one of the light portions passes while the other does not.
Up to now, the light guide and light source have been designed to minimise and substantially avoid reflections off the second opposed ends. In contrast, with this invention, we positively utilise those reflections to generate one or more further versions of the image to enable other characteristics of the image to be detected. This is particularly useful where substrates such as security documents are scanned since these will contain security feature such as features which fluoresce in the infra-red as well as features which are visible to the naked eye. With the invention, both types of feature can be detected substantially simultaneously by selectively filtering the light from each version of the image.
Typically, the second opposed ends will be substantially orthogonal to the parallel sides and may also be orthogonal to the first opposed ends. This simplifies the optical construction of the light guide.
The two portions of reflected light can be received by different parts of a single receiving device such as a linear CCD array or could be directed to different receiving devices which collectively form a “light receiver”.
In one example, one of the reflected portions of light is passed unfiltered to the light receiver while the other is selectively filtered prior to being received. In other examples, both portions could be filtered.
The light source will typically generate radiation in visible and invisible wavelength band, the invisible band being infrared or ultraviolet. However, other combinations are possible such as three or more wavelength bands (either all visible, all invisible or a mixture) or two visible wavelength bands, for example infrared and ultraviolet. The pass band(s) of the or each filter will be chosen accordingly.
The invention thus provides a scanning device, which is simple in design, provides high performance and high speed of operation at a low power of illumination to capture images on transported carriers, for example paper or plastics, and in particular security documents such as credit cards, identification cards and banknotes carried on a transport system, such as a banknote processing machine.
The use of a light guide of this form concentrates light from the light source on to the image carrier, thus enabling relatively weak sources to be used while at the same time providing a simple way of separating the transmitted and received light (and corresponding transmitting and receiving apparatuses) in a compact manner.
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patent: 59-39165 (1984-03-01), None
patent: 62-26971 (1987-02-01), None
patent: 2032217 C1 (1995-03-01), None
patent: 92/16909 (1992-10-01), None
patent: WO 94/19766 (1994-09-01), None
patent: WO 94/19764 (1994-09-01), None
patent: WO 99/18536 (1999-04-01), None
Frech Karl D.
Fureman Jared J.
Nauchno-Teknichesky Kooperative (Vector)
Oliff & Berridg,e PLC
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